Electric cutting system

ABSTRACT

An electric power saw/cutter includes a rotatable saw structure, a rear handle with a switch/speed control, a front handle and a drive unit for rotating the saw structure. The drive unit itself including a saw structure drive arrangement to which the saw structure is attachable, a transmission for driving the saw drive arrangement, an electric motor for driving an input shaft of the transmission, and a support structure for holding/carrying the saw structure drive arrangement, the transmission and the electric motor. The front handle and the rear handle are directly connected to each other to form a handle unit, which unit is resiliently connected to the drive unit, so that vibrations from the saw blade and drive unit will be reduced in the handle unit.

TECHNICAL FIELD

The invention is related an electric machine system and in particular anelectric cutting system at least comprising an electric power cutterwhich power cutter comprises a rotatable circular saw blade with aprotective cover, a rear handle with a switch/speed control and a fronthandle, a drive unit for rotating the saw blade, the drive unit itselfcomprising a saw blade drive shaft to which the saw blade is attachable,a transmission for driving the saw blade drive shaft, an electric motorfor driving an input shaft of the transmission and a support structurefor holding/carrying the saw blade drive shaft.

BACKGROUND ART

Electric power cutters normally have a front and a rear handle eachfirmly attached to a drive unit including an electric motor. Thisresults in that a lot of vibrations from the rotating tool and possiblythe motor reach the handles and the operator. In many countries dailyoperating times are reduced by regulations according to the measuredvibration level in the handle. It is known to attach one or both handlessomewhat flexible with rubber bushings. This does reduce vibrationlevels to a certain degree, but has a limited effectiveness.

Electric tools, of which many are hand-held, must meet manyrequirements. They must be powerful and durable, yet remain easy tohandle. A few of these tools are equipped with a high frequencybrushless asynchronous or synchronous motor which exhibits aspeed-torque characteristic that differs from ordinary AC motors tools.The speed of an asynchronous or synchronous motor at light loads isproportional to the frequency which also can be controlled to keep itsspeed relatively constant regardless of load conditions.

These motors are also known as brushless DC (BLDC) motors, and aregenerally reliable. Normally, they require a power supply device or apower converter, converting the mains frequency to the motor frequency,which often is higher than the mains frequency. The power converter isalso called frequency converter.

The power supply device provides a suitable voltage and frequency to thetool, where the rotational speed of the motor is determined by thefrequency of the supplied power. Such a power converter normallyconverts a mains input of, for example 3×400 V AC, 50 Hz, to athree-phase supply of 3×300 VAC, where the frequency is adjustable.

The power supply device or power converter is normally divided into twoparts—an input rectifier and an output inverter. If instead the BLDCmotor would be run from a DC source, e.g. a battery, no input rectifierwould be needed.

The input rectifier converts the incoming AC input voltage to a DCoutput voltage, often called DC bus voltage.

The output inverter converts the DC bus voltage to three-phase voltagesto the BLDC motor.

It is desirable for a tool with a BLDC motor to be able to operate overa broad range of AC mains voltages, e.g., from 3×180 VAC, 50/60 Hz, forthe Japanese market and nominally 3×400 VAC, 50 Hz, for the Europeanmarket. To achieve this, a power supply device according to the above isgenerally adopted to provide the same DC output voltage irrespective ofthe AC input. The common solution for this is to insert a converterassembly or voltage booster between the input rectifier and the outputinverter. The power supply device will then consist of the followingparts: Input rectifier, converter assembly or voltage booster and outputinverter. An example of this is described in, for example, WO2006009847.

The converter assembly or voltage booster converts (boosts) the incomingDC voltage to the output DC bus voltage, such that the output DC busvoltage normally is higher than, or the same as, the DC input voltage.Often the output DC bus voltage is a constant DC voltage, regardless ofthe input AC voltage.

However, there is still a need for an enhanced power supply device orpower converter, that may provide sufficient output power with smallerand less expensive components than those disclosed in the prior art.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a power supplydevice, that may provide sufficient output power with smaller and lessexpensive components than those disclosed in the prior art.

This object is obtained by means of a power supply device according toclaim 19.

It is an object of the invention to provide an improved electric cuttersystem which reduces vibrations in the handle unit from the cutterassembly during use. It is another purpose of the invention to providean electric cutter system which prevent scattering of dust when sawingin materials which have a tendency to generate dust. It is yet anotherpurpose of the invention to provide an electric cutter system which hasan efficient cooling system for cooling the electric motor.

According to the invention there is provided an electric powersaw/cutteras defined in claim 1. Hereby is achieved an electric powercutter where vibrations which unavoidably will be generated in the sawblade during sawing operation will be essentially reduced in the handleunit which is a significant advantage for the operator of the cutter.Not only will this reduce vibration-related health issues for users whofor example run cutting machines frequently and during extended timeperiods, it will also lead to that an operator may comfortably use themachine for longer time periods without risk being subjected toundesired vibration levels.

Further aspects of the cutting assembly, the cover device, the sealingbody, and the working machine, are apparent from the accompanying patentclaims and from the following description of preferred embodiments ofsaid devices. It shall be understood that terms like upwards anddownwards, upper surface, and bottom surface, respectively etc. refer toa cutting assembly with a cover device placed on a horizontal support.Further, the terms front and rear end mean the front end which is turnedin the direction in which one normally will work with the machine, andthe rear end, respectively, which rear end is positioned in the same endas the terminal member. The terms have been chosen in order tofacilitate the understanding of the description and does in no wayexclude working ceilings, vertical walls, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed description of the invention, reference willbe made to the accompanying drawings, in which:

FIG. 1 shows a schematic overview of an electric cutter system accordingto one embodiment of the invention.

FIG. 2 is a perspective view showing the power cutter according to oneembodiment.

FIG. 3 is another perspective view showing the power cutter of FIG. 2.

FIG. 4 is a perspective view showing the power cutter from the oppositeside compared to FIG. 3.

FIG. 5 is a perspective view of the power cutter shown without its sawblade.

FIGS. 6A-B show a cooling fluid system according to one embodiment ofthe invention.

FIGS. 7A-D show examples of distribution of cooling fluid through thecooling fluid system.

FIGS. 8A-C show a control unit for cooling fluid according to oneembodiment of the invention.

FIGS. 9A-B show detailed view of the control unit seen in FIGS. 8A-C.

FIG. 10 show a cross section of a motor according to a preferredembodiment.

FIGS. 11A-C shows various electric cutter machines.

FIG. 12 shows a schematic view of a power inlet, a power supply deviceincluding an input rectifier, a converter assembly, an output inverterand an electrically powered tool.

FIG. 13 shows a simplified schematic of the input rectifier comprised inthe power supply device of FIG. 12.

FIG. 14 shows a simplified schematic of a type of a converter assemblycomprised in the power supply device of FIG. 12.

FIG. 15 shows a simplified schematic of an alternative type of converterassembly comprised in the power supply device of FIG. 12.

FIG. 16 shows a schematic view of an alternative configuration for thepower supply device and the electrically powered tool shown in FIG. 12.

FIG. 17 shows a schematical illustration of power ports and voltages ina three-phase system.

FIG. 18 shows a schematic view of an alternative configuration for thepower supply device and the electrically powered tool shown in FIG. 12.

FIG. 19 shows a flowchart for a method enabling enhanced control andcommunication of available power.

FIG. 20 shows a cross section of the motor of FIG. 10 having axiallyspaced apart evacuations channels to provide an inner flow duringoperation of the motor.

FIG. 21 shows an embodiment of an inner tubular part of a motor housingaccording to one embodiment.

FIG. 22 shows an embodiment of the motor having the bearings axiallywithin the permanent magnets of the rotor.

DETAILED DESCRIPTION

FIG. 1 shows an electric tool in the form of an electric power cutter 1,an electric power supply device 100, and a fluid source 200 in the forma water tank. The electric power supply device 100 supplies powerthrough a cable 17 to the electric power cutter 1. It may also send dataand receive feedback data from the electric cutter 1 via the cable 17.The electric power supply device 100 connects to a power grid or agenerator via a residual current device 50. The electric power supplydevice 100 is described in more detail in relation to FIGS. 12-19.Cooling liquid, preferably cooling water, is fed from the fluid source200 to the electric power cutter 1 through hose 18.

The fluid source 200 is preferably a water tank with a low pressurepump, i.e. having a feeding pressure below 3 bar, preferably below 2bar, feeding cooling water to the motor 11 (see e.g. FIGS. 2-5) of theelectric power cutter 1 through hose 18.

A return conduit C may be connected to the motor 11 (see e.g. FIGS. 2-5)of the electric power cutter for return of the cooling water to thefluid source 200 in order to recirculate cooling water.

With reference now to FIGS. 2-5, the electric power cutter 1 accordingto the invention is generally designated 1 (the electric tool isdesignated 106 when referred to in relation to FIG. 12-19) and is shownfrom various perspective views. Its main parts comprise a cutterassembly 300, a drive unit 8 and a handle unit 4.

According to one embodiment the cutter assembly 300 includes a rotatablecircular saw structure, such as a saw blade 2, and preferably aprotective cover 3.

The drive unit 8 is arranged to rotate the saw blade 2, and comprises asaw structure drive arrangement 9 (e.g. a saw blade drive shaft 9) towhich the saw blade 2 is attachable, transmission 10 for driving the sawblade drive shaft 9, and a transmission drive source in the form of anelectric motor 11 (the motor is designated 136 when referred to inrelation to FIG. 12-19) for driving an input shaft of the transmission10. The drive unit 8 further includes a support structure 13 forholding/carrying the saw blade drive shaft 9, the transmission 10 andthe electric motor 11.

The transmission 10 may for instance be a gear train transmission, achain transmission, or a belt transmission. However the preferredtransmission is a belt transmission. The belt transmission, includingtransmission belt 10A, provides some slip if blade jams, i.e. overloadprevention and it is also quieter compared to other transmissionsolutions. The (input shaft 12)/(drive shaft 9) gear ratio is preferablywithin the range of 1:1 to 3:1, typically around 2:1.

The handle unit 4 includes a front handle 7 for carrying the saw and arear handle 5 for operating the saw. In one embodiment the handle unit 4comprises a cavity which houses the support structure 13 of the driveunit 8 in such a way that the motor 11 is essentially enclosed by thehandle unit 4. This is seen e.g. in FIGS. 2-3 where the motor 11 issubstantially covered by and therefore hidden behind the supportstructure 13.

The rear handle 5 is provided with a speed control trigger 6 for thedrive unit 8 and a trigger lock 15. The trigger lock 15 has to bepressed down to permit the speed control trigger 6 to move, therebypreventing an inadvertent activation of the motor 11. In a preferredembodiment the trigger lock 15 also functions as a cooling water supplycontrol in that the trigger lock 15, in addition to activating the speedcontrol trigger 6, also activates a fluid control unit 20 upon beingpressed down by an operator, meaning that an operator will activate bothof said speed control trigger 6 and the fluid control unit 20 (see FIG.6B) in the same grip around the rear handle 5. Thereby cooling water isenabled only when the electric motor 11 is running. The fluid controlunit 20 is further explained in FIG. 6B.

The electric power cutter 1 is connected to a fluid supply for coolingthe electric motor 11 and/or supplying fluid to the cutter assembly 300.In a preferred embodiment the fluid is water. Supplying water to thecutter assembly 300 provides cooling of the saw blade 2, and alsocontributes to prevent scattering of dust generated during workingoperation: water which is successively sprayed onto the saw blade 2,during use of the power cutter, binds the dust and thereby prevents itfrom being spread to ambient air.

Cooling water is fed to the electric power cutter 1 via hose 18 which isconnected to a fluid source 200 (see FIG. 1) e.g. to a water supplynetwork or to a water tank.

The cooling fluid system is generally designated 500, and will now befurther described with reference mainly to FIGS. 6-8 showing an overviewof a cooling water system 500 in accordance with an embodiment of theinvention.

FIG. 6A is an overview of a cooling fluid system 500 arranged to becoupled to an electric power cutter 1 according to the invention, and tosupply cooling fluid (e.g. water) to the motor 11 for cooling and to thecutter assembly 300 for cooling/preventing scattering of dust. Thecooling fluid system 500 comprises supply hose 18 which leads thecooling fluid (hereinafter also referred to as cooling water and/orcooling liquid) to a motor inlet 14 for cooling liquid. Further thewater cooling system 500 comprises a fluid control unit 20, a transferconduit A, a tool conduit B and a return conduit C.

As already mentioned, water is supplied to the electric cutter 1 bycoupling the supply hose 18 to a fluid source 200 e.g. a water tank orto a water supply network. Water is run through the hose 18 via saidmotor inlet 14 into the motor 11 for cooling. After having passedthrough the motor 11 the cooling water exits through a motor outlet 16and is transferred via transfer conduit A to the fluid control unit 20which regulates further distribution of the water. By means ofmanipulating the fluid control unit 20 water may be guided into toolconduit B for exit through at least one saw blade nozzle 21 or intoreturn conduit C for return of water e.g. to said fluid source 200 orfor discarding. The total amount of fluid passing through the system500, however, will always first pass through the motor 11 before beingtransferred to the tool conduit B or to the return conduit C. In oneembodiment it is also possible to completely seal off/close the fluidcontrol unit 20 so that no water will pass, neither to the tool conduitB nor to the return conduit C, as will later be described in moredetail.

FIG. 6B illustrates the function of said trigger lock 15 arranged toactivate supply of cooling liquid through the motor 11. The trigger lock15 is the distal end of a lever arm 30 pivotably secured at its proximalend 19 to the handle unit 4, and protruding from the rear handle 5 asseen e.g. in FIG. 2 and being located opposite to the sped controltrigger 6 so that an operator with one hand can push the trigger lock 15and operate the speed control trigger 6. The lever arm 30 is springbiased so that when released it returns to a position locking the speedcontrol trigger 6 and deactivating the fluid control unit 20. Whenpressing the trigger lock 15 towards the rear handle 5, the lever 30moves downwards in a pivoting movement. The downward movement of thelever arm 30 leads to that it will engage a closure member 22 of aninlet valve 23 of the fluid control unit 20 in such a way that pushingdown the closure member 22 opens the inlet valve 23 and permits water toflow from the transfer conduit A into the fluid control unit 20.Obviously, when water runs through the fluid control unit 20; waterflows through the motor 11.

Distribution routes of cooling liquid via the fluid control unit 20 aredescribed in the schematic illustrations of FIGS. 7A-D showing differentways of guiding the incoming water from the transfer conduit A. FIGS.7A-B show one example of arranging a control unit 20 according to theinvention and FIGS. 7C-D show another example.

Each of FIG. 7A-D displays transfer conduit A, tool conduit B and returnconduit C, as well as valves 23, 24, 25 arranged in the fluid controlunit 20 by means of which water distribution can be manipulated. Saidvalves includes a first 23 valve (also referred to as inlet valve 23), asecond valve 24 (also referred to as tool conduit valve 24) and a thirdvalve 25 (also referred to as return conduit valve 25).

FIGS. 7A-B show one example of arranging the valves 23, 24, 25 of thefluid control unit 20. According to this embodiment the fluid supply tothe blade 2 is independent of the fluid return to return conduit C, i.e.regulation of the flow to the blade not affected by opening/closing thereturn valve 25. FIG. 7A illustrates a configuration wherein all thefluid passing the system is guided to the tool conduit B by means ofopen first 23 and second 24 valves and closed third valve 25. In FIG. 7Bthere is illustrated a configuration where all the fluid passing thesystem is guided to the return conduit C by means of open first 23 andthird 25 valves and closed second valve 24.

The valve arrangement shown in FIGS. 7A-B means that fluid may besupplied both to the tool conduit B and to the return conduit C at thesame time, i.e. by opening both of the respective second 24 and third 25valves.

FIG. 7C illustrates a situation where the inlet valve 23 is open and thefluid control unit 20 set to allow water supply only to the tool conduitB by opening the tool conduit valve 24 and closing the return conduitvalve 25. The return conduit valve 25 could however be provided with athrough channel 250, as shown in FIG. 7A, arranged to allow for passageof a predetermined volume of water and by blocking the through channel250 the return conduit valve 25 is closed. In one embodiment such volumecorresponds to a flow rate between 0.3-0.7 Lit/min, preferably 0.4-0.6Lit/min. As an example, if said flow rate equals 0.5 Lit/min and wateris supplied from a tank comprising 15 Lit, the time to circulate theentire amount of the water from said tank through the cooling fluidsystem 500 once would equal 30 minutes.

In the shown embodiment the tool conduit valve 24 can be graduallyopened/closed meaning that the amount of water which is supplied to theblade 2 can be adjusted by opening/closing the tool conduit valve 24 tovarious degrees. Regulation of water to the blade 2 also affects thevolume of cooling water passing through the motor 11: maximum opening ofthe second valve 24 leads to maximum cooling of the motor and viceversa. The valves 23, 24, 25 of the fluid control unit 20 can preferablybe opened/closed independently of each other, meaning that for instancein FIG. 7C the tool conduit valve 24 can be closed (as shown in dashedlines) to completely stop water from passing through the fluid controlunit 20 regardless of whether the inlet valve 23 is open or closed.Closing of both second 24 and third 25 valves leads to working operationwith dry cutting blade 2 and no cooling of the motor 11 (i.e. stoppedflow of cooling liquid) since liquid is prevented from passing throughthe fluid control unit 20.

FIG. 7D illustrates a situation where both the first inlet valve 23 andthe third return conduit valve 25 are open, meaning the fluid controlunit 20 is set to allow water supply only to the return conduit C andnot to the blade. In one embodiment the return conduit valve 25 is anon/off valve meaning it can either be set at a fully open or a closedmode. As shown in FIGS. 7A-B opening of the third valve 25simultaneously leads to sealing of the passage to the tool conduit B,meaning that flow of water to the return conduit C also leads to thatthe water supply to the tool conduit B is shut off. Opening of the thirdvalve 25, as in FIG. 7D, thus leads to working operation with a drycutting blade 2 and cooling of the motor 11 by means of liquid runningthrough the motor 11 via the transfer conduit A and further passing thefirst 23 and third 25 valves into the return conduit C. Thus by openingthe return conduit valve 25 an operator may shut off water supply to theblade and still keep cooling fluid running through the motor 11 in justone movement (i.e. switch open the return conduit valve 25).

By optionally having a channel 250 a, as shown by the dotted box X, aminimum flow through the fluid control unit 20 can be guaranteed aslongs as the inlet valve 23 is open.

The fluid control unit 20 according to one embodiment of the inventionis shown in more detail in FIGS. 8A-C, where FIG. 8A is a perspectiveview of the fluid control unit 20 and FIGS. 8B and 8C show various crosssections intended to illustrate the fluid control unit 20. The valves ofthe fluid control unit 20 shown in FIGS. 8A-C are arranged asschematically illustrated in FIGS. 7A-B. The position of the fluidcontrol unit 20 in the cooling fluid system 500 is seen in FIG. 6A, andFIG. 6B shows the position of the fluid control unit body 27 in relationto the lever arm 30.

The fluid control unit 20 comprises body 27 housing a first inlet valve23, a second tool conduit valve 24 and a third return conduit valve 25.Preferably both the inlet valve 23 and the return conduit valve 25 areon/off valves and are based on the same type of valve mechanism (thereturn conduit valve 25 is described e.g. in FIG. 9A-B) and preferablythe tool conduit valve 24 is a gradually adjustable restriction valve.Fluid is supplied to the fluid control unit 20 through the transferconduit A which is connected to an inlet port 40 leading to the inletvalve 23. Fluid can exit the fluid control unit 20 through the toolconduit valve 24 leading to a tool conduit port 41 which is connected tothe tool conduit B, and/or through the return conduit valve 25 leadingto a return conduit port 42 which is connected to the return conduit C.Fluid flowing through tool conduit B will finally exit through the sawblade nozzles 21 onto the blade 2 cooling the blade 2 as well asreducing dust in the air by wetting it. Fluid flowing through returnconduit C could be discarded or be returned to the fluid source 200 forrecycling. For instance the fluid source 200 could be a bucket fromwhich water is pumped to flow through the system.

The inlet valve 23 includes an inlet valve closure member 22 which canmove between an open and closed position. A spring 35 urges the inletvalve closure member 22 to a closed position. In the closed position oneend of the inlet valve closure member 22 protrudes from the body 27 andby pushing the protruding end of the inlet valve closure member 22 in adirection towards the body 27 the inlet valve closure member 22 can bemoved to a position opening the inlet valve 23. Upon releasing thepressure of the protruding end, the inlet valve closure member 22 isurged by the spring 35 in the opposite direction closing the inlet valve23.

Activation of the cooling water supply is accomplished by pressing downthe trigger lock 15 so that the lever arm 30 presses the protruding endof the inlet valve closure member 22 thereby opening the first inletvalve 23 of the fluid control unit 20. Once the first valve 23 is openwater is guided via inner channels (not shown) through the body 27 untilit reaches an inner chamber 270 inside the body 27. The inner chamber270 is arranged with two exits/outlets whereof one leads to the toolconduit valve 24 and the other to the return conduit valve 25, forexiting fluid through the tool conduit port 41 and/or return conduitport 42.

If the return conduit valve 25 is set to open mode water may exit theinner chamber 270 and pass the return conduit valve 25 into the returnconduit C. In the shown embodiment the return conduit valve 25 is of thesame type as the inlet valve 22, having a return conduit valve closuremember 28 which can move between an open and closed position. A spring253 urges the return conduit valve closure member 28 to a closedposition. The return conduit valve closure member 28 is controlled by aswitch 29 (see e.g. FIG. 6B) that can be turned between two positions, afirst position pressing a protruding end of the return conduit valveclosure member 28 towards the body 27 thereby moving the return conduitvalve closure member 28 to a closed position, and a second positionreleasing pressure on the protruding end allowing the spring 253 to movethe return conduit valve closure member 28 to a closed position. Themechanism of opening/closing of the return conduit valve 25 is furtherclarified in FIGS. 9A-B.

Opening/closing of the tool conduit valve 24 is achieved by manipulatinga water control knob 26 to increase or decrease the passage area throughthe valve 24 thereby being able to gradually adjust the amount of waterrunning through the valve passage and into the tool conduit B via thetool conduit port 41 to finally exit through the saw blade nozzles 21onto the blade 2. The knob 26 comprises an elongated portion 260provided with outer threads, which elongated portion 260 is intended tobe inserted into a matching opening 261 (see also FIG. 6B) in the body27 of the fluid control unit 20, said opening 261 comprising innerthreads matching the outer threads of said elongated portion 260. InFIG. 8C there is seen the knob 26 positioned with its elongated portioninside said opening 261. The cone-shaped outermost end 262 of theelongated portion 260 is arranged at the outlet of said inner chamber270 leading to the tool conduit port 41. The cone-shaped portion of theoutermost end 262 is arranged inside the outlet creating a restrictionpassage which can be adjusted to allow for passage of more or less fluidby displacing the elongated portion 260, which is achieved bymanipulating the knob 26.

When turning the knob 26 the outer threads of the elongated portion 260will interact with the inner threads of the opening 261 so that theelongated portion is displaced in the opening 261. To close the toolconduit valve 24 the knob 26 is turned to such a position that saidoutermost cone-shaped end 262 tightly seals the outlet of the innerchamber 270, thereby blocking any water from passing into the toolconduit B. In a corresponding way the tool conduit valve 24 is opened bymeans of turning the knob 26 to displace the elongated portion 260 toopen the outlet thereby allowing fluid to exit the inner chamber 270 andenter the tool conduit B via the tool conduit port 41. The amount ofwater which may exit the chamber 270 can be adjusted by controlling theposition of the cone-shaped end portion 262 in relation to the outlet:the closer the cone-shaped end portion 262 is brought to a sealedposition the less fluid will be able to pass and vice versa.

If the tool conduit valve 24 as well as the return conduit valve 25 arein closed mode water is prevented from passing the fluid control unit 20and no cooling liquid will flow through the motor 11.

FIGS. 9A-B show detailed views of a fluid control unit 20 in crosssection, illustrating the function of a return conduit valve 25according to the embodiment of FIGS. 8A-C. FIG. 9A shows the returnconduit valve 25 in closed mode and FIG. 9B shows the return conduitvalve 25 in an open mode. The skilled person understands that thesolution described in FIGS. 9A-B represents one of many possibilities ofacquiring the desired valve function.

The return conduit valve 25 comprises a spring biased closure member 28arranged with a sealing member 251, such as a sealing ring 251. When thevalve 25 is in a closed mode (FIG. 9A) the spring 253 acts on theclosure member 28 so that the sealing member 251 sealingly abuts aninner flange 252 preventing passage of fluid. Activating the returnvalve (e.g. by means of said switch 29) is achieved by pushing theclosure member 28 inwards as indicated with arrow 31 seen in FIG. 9B,overcoming the pressure from the spring 253. The closure member 28 iskept in the activated position for instance by means of letting saidswitch 29 (e.g. shown in FIG. 6B) block the closure member 28 so that itremains in the corresponding activated position. In an activatedposition the sealing member 251 has been displaced upwards so that a gapis created between the closure member 28 and the inner flange 252allowing for passage of fluid into the return conduit C via the returnconduit port 42. The flow through the open return conduit valve 25 isindicated with arrows 32 in FIG. 9B.

The electric power cutter 1 further comprises an anti-vibration handlesystem 400. The handle unit 4 is resiliently connected to the drive unit8 via said anti-vibration handle system 400 so that vibrations from thesaw blade 2 and drive unit Swill be reduced in the handle unit 4.Essentially all vibrations will come from the saw blade 2 since thepower source is an electric motor 11. Said anti-vibration handle system400 includes a number of vibration damping elements, preferably at leastthree vibration damping elements 401, 402, 403, 404 arranged in betweenthe handle unit 4 and the support structure 13 of the drive unit 8. Anuppermost first vibration element 401 is connected to the front handle 7vertically above the motor 11. Longitudinally the first vibrationelement 401 is located in between a forward most vibration element/s403, 404 and a rearward most vibration element 402. Both the forwardmost vibration element/s 403, 404 and the rearward most vibrationelement 402 are located vertically below the motor 11, forming atriangle seen from a side perspective. The rearward most vibrationelement 402 is connected to the rear handle 5 behind the motor 11whereas the forward most vibration element/s 403, 404 are connected infront of the motor 11 but rearward the saw blade 2. The forward mostvibration element/s 403, 404 are two vibration elements connecting froma first lateral side of the support structure 13, respective secondlateral side of the support structure 13 to a same position on thehandle unit 4 laterally in-between. In a preferred embodiment saidvibration damping elements are in the form of resilient coil springs,however also other types of damping elements are conceivable such asrubber elements.

FIG. 10 shows a high frequency permanent magnet motor 11 according to anembodiment of the invention. The motor 11 is suitably for poweringelectric cutter 1: However, it could also be used in other applicationswhere an electric HF motor is desirable.

The motor 11 is a synchronous motor and includes a motor housing 52 a,52 b, ball bearings 63 a, 63 b that supports an inner rotor 51, and anouter stator 54 that surrounds the inner rotor 51 and being supported bythe motor housing 52 a, 52 b. The stator 54 includes an iron core withthree phase windings 68 that generate a rotating magnetic field whenpowered. A box 65 for electrical connections is located at one axial endof the motor 11.

The inner rotor 51 includes a rotor body 64, and a plurality ofpermanent magnets 56 arranged at the outermost radius of the rotor body.By having the magnets 56 at the outermost radius of the rotor body 64the torque of the motor is higher than if they were placed closer to therotational axis, i.e. the further away from the rotational axis thehigher the torque of the motor 11 gets. Furthermore increasing numbersof magnets 56 around the rotor body 64 also increases the torque.Preferably the number of permanent magnets 56 around the rotor body 64is within the range of 4-20, more preferably 6-16, most preferably 8-12.This enables a sufficiently high torque at a comparably low motor speedso that a gear ratio can be around 2:1 can be employed, thereby enablingthe use of a belt transmission. The permanent magnets 56 are arranged inpairs, positioned opposite to each other at the outermost radius of therotor body 64. The shown embodiment has 5 pole pairs. To get a speed of100 revolutions per second you would need to feed 500 Hz (100×5).

The permanents magnets 56 may be glued to the rotor body 64 andadditionally secured by ribbons (not shown), e.g. glass fiber ribbons orcarbon fiber ribbons, wound around the rotor body 64 and the magnets 56.The magnets 56 can of course be secured to the rotor body 64 by othermeans, e.g. a plastic or metal tube pressing the magnets 56 to the rotorbody 64. The magnets 56 may also be sintered to the rotor body 64.

The motor 11 is fed by an electric a power supply device 100. In anotherembodiment the power supply device 100 is an electric second motor ofthe same configuration as the motor 11. The difference is that it is runas a generator. The generator may be driven by a combustion engine,solar power, wind turbine, water turbine, batteries, fuel cells, nuclearenergy, etc. By having the generator being of the same configuration asthe motor 11, there is no need to transform the phases, since they areperfectly matched.

The rotor body 64 has a central cavity 57 which is accessible from theexterior via a plug 62 at one axial end of the rotor 51, defining anupper end of the cavity, and extending along the rotational axis of therotor to the opposite axial end where a bottom end of the cavity isformed. The opposite axial end of the rotor body 64 further includes abore 66 to which the input shaft of the transmission can be secured. Thecavity 57 has a circular cross-section that is symmetric around therotor axis, but the diameter of the cavity 57 may vary along the lengthof the cavity 57. A number of first evacuation channel/s 58 a extends ina radial direction through the rotor body 64 from the bottom part of thecavity 57 towards the periphery of rotor body 64. The first evacuationchannels 58 a are preferably two and extending in opposite directions tomaintain rotational symmetry. However, only one first evacuation channel58 a may be conceivable by balancing the rotor 51 by other means thanretinal symmetry. More than two first evacuations channels 58 a are alsofeasible. The central cavity 57 and the first evacuation channels 58 adefining an inner volume 57, 58 a of the motor 11.

An outer volume 59, 60, 61 of the motor 11 is defined by all voidsoutside the rotor 51 that are fluidly connected to the rotor cavity. Inparticular, a gap 59 between the rotor 51 and the stator 54, andoptionally the spaces 60, 61 around the axial ends of the stator 54. Thespaces 60, 61 around the axial ends of the stator 54 are preferablyfluidly connected to the gap 59 and the inner cavity 57. It is howeverpossibly that the spaces 60, 61 around the axial ends of the stator 54are closed and not fluidly connected the gap 59 and inner cavity 57. Insuch embodiment it is possible to supply one oil, e.g. transformer oil,to the spaces 60, 61 around the axial ends of the stator 54, anddifferent oil, e.g. lubricating oil, to the rotor cavity 57 and theouter volume connected thereto. Although it is preferred to supply oilto the interior of the motor it may be possible to replace the oil withother liquids.

The cavity 57 being is connected to the outer volume 59-61 by at leastone first evacuation channel 58 a which runs in a radial directionthrough the rotor body 64, preferably at least one pair of firstevacuation channels 58 a that are arranged rotational symmetric. At anupper end of the cavity 57, i.e. the end where the plug 62 is situated,there is provided at least one passage 67 connecting the upper end ofinner cavity 47 to the outer volume 59, 60, 61. The passage 67 ispreferably a recess or groove in the motor housing 57 in the region ofthe bearing 63 a.

Preferably the interior of the motor 11 is filled with the oil byopening the plug 62 and pouring oil to the inner cavity 57. When pouringoil into the inner cavity, the oil will flow out to the outer volume59-61 through the first evacuations channel/s 58 a. Air in the outervolume 59-61 will gradually evacuate through the passage 67 and out viathe plug opening as oil is filled.

For optimal cooling of the motor 11 the volume of the oil, supplied (theoil volume defined at an temperature of 23° C.) to the interior of themotor 11 corresponds to at least 50% of the outer volume 59-61, morepreferably at least 80%, most preferably at least 100%. Preferably theoil volume fills 20-80% of the entire volume 57-61, i.e. the innervolume 57, 58 a and the outer volume 59-61.

When the motor is run and the rotor 51 rotates, oil present in thecavity 57 will be urged by centrifugal forces through the channels 58 atowards the outer volume 59-61, thereby at least partially filling theouter volume 59-61 with oil, preferably entirely filling the outervolume 59-61 with oil.

However, the entire volume 57-61 should not be fully filled with oil. Onthe contrary it is desirable to have an air pocket to reduce thepressure build up from oil expansion as it is heated. The purpose of theinner cavity 57 is to provide such an air pocket. At an oil temperatureof 23° C., it is preferred that the air volume present in the entirevolume, i.e. inner and outer volumes, corresponds to at least 25% of theinner cavity 57, preferably at least 50%, most preferably at least 80%.Furthermore, the inner cavity's 57 share of the entire volume 57-61 ispreferably within the range of 10-90% of the entire volume 57-61,preferably within 25-60%. The entire volume 57-61 is preferably withinthe range of 50-300 ccm. Preferably the cavity 57 having a volume of25-150 ccm.

The motor housing 52 a, 52 b includes two tubular parts, an innertubular part 52 a and an outer tubular part 52 b, both having one axialend closed and the opposite open. The diameter of the inner tubular part52 a is somewhat smaller than that of the outer tubular part 52 b sothat the inner tubular part 52 a can be inserted into the outer tubularpart 52 b, respective open end facing each other, to provide acylindrical shaped motor housing 52 a, 52 b. The inner tubular part 52 ahas a groove running around its outer curved surface 43 forming acooling path 55 within the side wall 45 of the motor housing 52 a, 52 bthat is parallel to the rotor axis. The side wall 45 in the presentapplication refers to the curved wall between the axial ends. Thecooling path 55 has a shape of a circular helix and includes an inlet(14 in FIG. 6A) at one axial end of the motor housing 52 a, 52 b and anoutlet (16 in FIG. 6A) at the opposite axial end. The inlet and theoutlet provided in the outer tubular part 52 b of the motor housing.Thereby the side wall 45 of the motor 11 can be actively cooled by aliquid flow.

To increase cooling performance the motor housing 52 a, 52 b ispreferably made in a material being a good thermal conductor, forinstance aluminum.

FIG. 20 shows a high frequency permanent magnet motor 11 according toanother embodiment of the invention. The motor 11 is identical to thatshown in FIG. 10 apart from that the cavity 57 includes a number ofsecond evacuation channel/s 58 b axially spaced apart from the firstevacuation channel/s 58 a and connecting to the outer volume 59-61 atthe opposite axial end of the cavity 57.

The first evacuation channel/s 58 a are configured to provide a strongerpump effect when the rotor is rotated than that of the second evacuationchannel/s 58 b in order to create a pump effect when rotating the rotor,thereby providing a flow inside the motor with one flow direction withinthe cavity 57 and the opposite flow direction in the gap 59.

In the shown embodiment the stronger pump effect is provide byconnecting the first evacuation channel/s 58 a to the outer volume 59-61at a radial distance further away from the rotational axis than theradial distance that the second evacuation channel/s 58 b connects tothe outer volume 59-61. Other means of achieving a difference in pumpeffect can of course be implemented. Furthermore the second evacuationchannel/s 58 b may alternatively be configured to provide a strongerpump effect when the rotor is rotated than that of the first evacuationchannel/s 58 a.

FIG. 21 shows an embodiment of the inner tubular part of the motorhousing of FIG. 10. In FIG. 21 the reference number 1052 a is used forthe inner tubular part whereas 52 a is used in FIG. 10. The innertubular part 1052 a mates with the outer tubular part 52 b in the samemanner as described in relation to FIG. 10 providing a cylindrical motorhousing 1052 a, 52 b.

A cooling path 1055 is formed by an outer groove on the outer curvedsurface 1043 of the inner tubular part 1052 a. The cooling path 1055runs back and forth in the axial direction forming a meander patternbetween the two tubular parts 1052 a, 52 b, i.e. within the side wall 45of the motor housing 1052 a, 52 b.

The cooling path 1055 includes a plurality of first cooling sections1055 a running in a direction parallel to the rotor axis and beingessentially equidistantly distributed at a predetermined radius from therotor axis, and a plurality of second and third cooling sections 1055 b,1055 c. The second cooling sections 1055 b connecting two adjacent firstcooling sections at one axial end thereof, and the third coolingsections 1055 c connecting two adjacent first cooling sections at theopposite axial end, in such manner that the second and the third coolingsections 1055 b, 1055 c never connect the same pair of first coolingsections. Thereby the meander pattern is formed.

The inner tubular part 1052 a further includes a at least one innergroove 1069 (here exemplified by ten inner grooves) spatially arrangedbetween two adjacent first cooling sections 1055 a and running in adirection parallel to the rotor axis. The at least one inner groove ispreferably a plurality of inner groves; more preferably the number ofinner grooves are within the range of 5-20. The inner grooves 1069 aredistributed around the inner curved surface 1044 of the inner tubularpart, which also is the inner curved of the motor housing 1052 a; 52 b,in such way that two first cooling sections 1055 a are located betweentwo adjacent inner grooves 1069. This makes it inner and outer groovescan be incorporated without requiring too large wall thickness of theinner tubular part 1052 a

Preferably the inner groove/s 1069 extends between the axial ends ofstator 54 and is fluidly in contact with the outer volume 59-61.

In FIG. 22 is shown an embodiment of the motor. For similar parts thesame numbers have been used as of FIG. 10 but in the 2000-series. Thusthe motor is designated 2011 and includes a motor housing 2052 a, 2052b. An outer stator 2054 in the motor housing surrounds an inner rotor2051 having permanent magnets 2056 arranged at its outer radius. Therotor 2051 is supported by bearings 2063 a, 2063 b at each axial end ofthe rotor 2051. The bearings 2063 a, 2063 b are located within the axialoutermost permanent magnets 2056′ of the rotor 2051. Thereby the axialextension of the motor 2011 can be minimised.

The axial length is preferably reduced by having the bearings and therotor are arranged so that at least 50% of their axial length extendswithin the axial outermost permanent magnets 2056′ of the rotor 2051,more preferably at least 80%, most preferably at least 90%.

FIG. 11a shows an electric power saw/cutter 1 where the rotatable sawstructure 2 is a ring saw blade 71 and the saw structure drivearrangement 9 is a ring saw aggregate 72 a, 72 b.

FIG. 11b shows an electric power saw/cutter 1 where the rotatable sawstructure 2 is two circular saw blades 81, 82 at an axial distance fromeach other and the saw structure drive arrangement 9 is a common sawblade drive shaft 83 driving both saw blades 81, 82.

FIG. 11c shows an electric power saw/cutter 1 where the rotatable sawstructure 2 is a saw chain 91 and the saw structure drive arrangement 9is a saw chain sword 92 and a chain drive wheel 93 making the saw chainrotate around the sword 92.

With reference to FIG. 12 and FIG. 13, an electrically powered tool 106and a power supply device 100 are shown schematically. The tool is forexample an electric cutter or an electric drill motor. The tool 106comprises a synchronous motor 136 which is fed with power from a powersupply device. The power supply device 100 comprises a power input 102and a tool interface 103, where the power input 102 is arranged to beconnected to a power source inlet 104, such as an AC mains inlet. Inthis example, the power input 102 comprises three alternating currentpower ports 110, 111, 112. The tool interface 103, comprising a poweroutput 105, is arranged to be connected to an electrically powered tool106. The power output 105 is arranged to provide an alternating voltageV_(tool) with a certain controllable frequency f_(tool) to theelectrically powered tool 106. Further between power input 102 and poweroutput 105 the power supply device of FIG. 12 comprises three mainparts: an input rectifier 107, a converter assembly 133; 133′ and anoutput inverter 135. It is to be understood that in other variants one,two or all of these parts could be included in the power tool 106instead. It is also to be noted that all connections shown in FIG. 12are of a schematic nature, and may comprise two or more separateelectric conductors each, as is evident from the context.

The tool interface 103 also comprises a communication interface 138,arranged for communicating with the tool 106. For this purpose, the tool106 comprises a tool communication interface 139. In order to controlall communication between the power supply device 100 and the tool 106,the power supply device 100 comprises a control unit 134 and the tool106 comprises a tool control unit 140.

For example, if a user presses a speed button on the tool 106, the toolsends a request for increased output frequency to the control unit 134in the power supply device 100 via the communication interface 138. Thecontrol unit 134 then controls a frequency increase of the controllablefrequency f_(tool). Other communication may for example compriseidentification of the tool 106 presently connected to the power supplydevice 100.

According to the present invention, the power input 102 comprises aneutral port 113 which is connected to a voltage that in normalconditions is the average of the voltages of said alternating currentpower ports. In this example, the neutral port 113 is connected to ajunction J between the alternating current power ports 110, 111, 112,where the current equals zero at an even load.

Using the neutral connection is advantageous since it enables anenhanced performance if power is lost at one or more of the alternatingcurrent power ports 110, 111, 112 compared to with the case where aneutral connection is not used. As an example, the use of the neutralconnection results in resulting remaining a power of 75% instead of 50%if power is lost at one of the alternating current power ports 110, 111,112, and a resulting remaining a power of 40% instead of 0% if power islost at two of the alternating current power ports 110, 111, 112. Thefigures are approximate, but indicate the magnitude of this advantage.

The power supply device 100 further comprises an input rectifier 107that is connected to the power input 102 and comprises a positive outputline 108 and a negative output line 109. The input rectifier 107 furthercomprises a first set 114 a of rectifying diodes connected between, onone hand, the alternating current power ports 110, 111, 112 and theneutral port 113, and, on the other hand, the positive output line 108.The input rectifier 107 also comprises a second set 114 b of rectifyingdiodes connected between, on one hand, the alternating current powerports 110, 111, 112 and the neutral port 113, and, on the other hand,the negative output line 109. A smoothing capacitor 144 is connectedbetween the output lines 108, 109.

As shown in FIG. 13, the neutral port 113 is connected to a firstrectifying diode 149 which is connected to the positive output line 108,and to a second rectifying diode 150 which is connected to the negativeoutput line 109. The first rectifying diode 149 is comprised in thefirst set 114 a of rectifying diodes and the second rectifying diode 150is comprised in the second set 114 b of rectifying diodes.

According to another aspect of the present invention, also withreference to FIG. 14, the power supply device 100 comprises a converterassembly 133 which in turn comprises a first converter unit 115 and asecond converter unit 116. Each converter unit 115, 116 comprises arespective first inductance 117 and second inductance 118 connected inseries between an input rectifier output line 108, 109 and a respectivefirst rectifying device 119 and second rectifying device 120. Eachconverter unit 115, 116 also comprises a respective first controllableswitch device 121 and second controllable switch device 122 and also arespective first capacitance 123 and second capacitance 124. Thecontrollable switch devices 121, 122 and the capacitances 123, 124 areconnected in parallel over the respective rectifying device 119, 120.

The converter units 115, 116 are connected to each other such that theparallel connections of the respective controllable switch devices 121,122 and capacitances 123, 124 are connected in series, the voltage overthe capacitances 123, 124 constituting an output DC bus voltageV_(DCBus). Each controllable switch device 121, 122 is arranged tocontrol charge and discharge of electrical energy to and from itscorresponding inductance 117, 118 such that the output DC bus voltageV_(DCBus) is maintained at a desired level.

In this example, the rectifying devices 119, 120 are in the form ofdiodes, and the controllable switch devices 121, 122 are in the form oftransistors. In order to control the switching properties of eachtransistor 121, 122, each transistor 121, 122 comprises a correspondingcontrol port 141, 142 that is connected to the control unit 134.

In this example, the power supply device 100 thus comprises a converterassembly 133 which in turn comprises a first converter unit 115 and asecond converter unit 116, where the first converter unit 115 and asecond converter unit 116 are mutually mirrored in an imaginary symmetryline 143 indicated in FIG. 14.

The use of a converter assembly 133 is advantageous since it enablesdifferent power inputs, even a single phase power source may be used bymeans of a hardware adapter. For example, in Japan a common suppliedvoltage is 3×180 V AC and in Europe a common supplied voltage is 3×400 VAC or 1×230 V AC. Input frequencies may also vary, in Europe it is 50 Hzand in the United States it is 60 Hz. The use of a converter assembly133 is also advantageous since it enables a more even currentconsumption.

The mirror coupling of two converter units 115, 116 within the converterassembly 133 is advantageous since it enables the use of components withlower power ratings, for example the capacitances 123, 124. Componentswith lower power ratings are more efficient and less expensive.Furthermore, the mirror coupling also provides an automatic balance ofthe output DC bus voltage V_(DCBus) over the capacitances 123, 124.

According to another example, with reference to FIG. 15, an alternativeconverter assembly 133′ further comprises a first parallel converterunit 125 and a second parallel converter unit 126. Each parallelconverter unit 125, 126 comprises a respective first parallel inductance127 and second parallel inductance 128 connected in series with arespective first parallel rectifying device 129 and second parallelrectifying device 130. Each parallel converter unit 125, 126 alsocomprises a respective first parallel controllable switch device 131 andsecond parallel controllable switch device 132. The first parallelcontrollable switch device 131 is connected between said first parallelinductance 127 and said first parallel rectifying device 129, and thesecond parallel controllable switch device 132 is connected between saidsecond parallel inductance 128 and said second parallel rectifyingdevice 130.

The first parallel converter unit 125 is connected in parallel with thefirst converter unit 115, and the second parallel converter unit 126 isconnected in parallel with the first converter unit 116 such that therectifying devices 119, 129 and the controllable switch devices 121, 131of the first converter unit 115 and the first parallel converter unit125 are connected over the capacitance 123 of the first converter unit115. In the same way, the rectifying devices 120, 130 and thecontrollable switch devices 122, 132 of the second converter unit 116and the second parallel converter unit 126 are connected over thecapacitance 124 of the second converter unit 116.

In this example, the rectifying devices 119, 120; 129, 130 are in theform of diodes, and the controllable switch devices 121, 122; 131, 132are in the form of transistors. In order to control the switchingproperties of each transistor 121, 122; 131, 132, each transistor 121,122; 131, 132 comprises a corresponding control port 141, 142; 145, 146that is connected to the control unit 134.

In this example, the power supply device 100 thus comprises analternative converter assembly 133′ which in turn comprises the firstconverter unit 115, the first parallel converter unit 125, the secondconverter unit 116 and the second parallel converter unit 126. The firstconverter unit 115 and the first parallel converter unit 125 areessentially connected in parallel, and the second converter unit 116 andthe second parallel converter unit 126 are essentially connected inparallel. The first converter units 115, 125 and the second converterunits 116, 126 are mutually mirrored in an imaginary symmetry line 143′indicated in FIG. 15.

A reason for having four converter units 115, 116; 125, 126 connectedaccording to the above is that this enables a better handling ofpossible relative large currents where the input voltage may be relativelow.

For all examples above, the power supply device 100 comprises an outputpower converter 135, arranged to convert the output DC bus voltageV_(DCBus) to an AC voltage V_(tool) suitable for the electric motor 136,the AC voltage having a frequency f_(tool) that corresponds to thedesired rotational speed of the electrically powered tool 106. Theoutput power converter 135 is for example in the form of an insulatedgate bipolar transistor, IGBT, converter, which is previously known. Itis also known that instead of using IGBT transistors the converter canuse metal over semiconductor field effect transistors, MOSFETs. As anexample, the output AC voltage V_(tool) may comprise three alternatingcurrent phases with an output voltage of 690 V peak to peak. The outputpower converter 135 may furthermore be arranged to provide a soft startby means of a controlled increase of the output frequency f_(tool) tothe presently desired value.

Furthermore, the power supply device 100 comprises a braking resistorassembly 137 that is arranged to be engaged in dependence of the outputDC bus voltage V_(DCBus). More in detail, according to an exampleillustrating the function of the braking resistor assembly 137, theoutput is normally 750 V DC.

-   -   1. The converter assembly 133; 133′ is disengaged if V_(DCBus)        exceeds 780 V DC.    -   2. the braking resistor assembly 137 is engaged when V_(DCBus)        exceeds 800 V DC, and    -   3. the motor brake is disengaged when V_(DCBus) exceeds 820 V        DC.

The above also works in the reverse order if the output DC bus voltageV_(DCBus) starts to fall.

In the general case the converter assembly (133; 133′) is disengaged ata first threshold value for the DC bus voltage (V_(DCBus)), and thebraking resistor assembly 37 is engaged at a second threshold value forthe DC bus voltage V_(DCBus). In the example above, the second thresholdvalue exceeds the first threshold value.

It is possible that the converter assembly 133; 133′ is disengaged andthe braking resistor assembly 137 is engaged at the same value of the DCbus voltage V_(DCBus), i.e. that the second threshold value is equal tothe first threshold value.

Generally, the power input for generating the DC bus voltage (V_(DCBus))is arranged to be decreased or disengaged in dependence of the output DCbus voltage (V_(DCBus)).

With reference to FIG. 16, an alternative configuration for the powersupply device 100′ and the electrically powered tool 106′ is shown.Here, the power supply device 100′ comprises a tool interface 103′ whichis arranged to supply a DC bus voltage (V_(DCBus)) to a brushless directcurrent (BLDC) motor 151. The BLDC motor 151 comprises an electric motor136 and an output power converter 135 according to the above. As in theprevious case, the output power converter 135 is arranged to convert theDC bus voltage V_(DCBus) to an AC voltage V_(tool) suitable for theelectric motor 136, the AC voltage having a frequency (f_(tool)) thatcorresponds to the desired rotational speed of the BLDC motor (51).Thus, in this case, the tool 106′ also comprises the output powerconverter 135, where the output power converter 135 and the electricmotor 136 together form the BLDC motor 151.

In this case, the power supply device 100′ comprises a DC power output148 arranged for outputting the DC bus voltage V_(DCBus) to the tool106′, and the output power converter 135 has a power output 105′arranged for outputting the alternating voltage V_(tool) with thecontrollable frequency f_(tool) to the motor 136′. Here, the outputpower converter 135 is shown connected to the tool control unit 140, andit is conceivable that the tool control unit 140 either by itself, ortogether with the control unit 134 in the power supply device 100′,controls the output power converter 135. It is also possible that onlythe control unit 134 in the power supply device 100′ controls the outputpower converter 135.

The present invention is not limited to the above, but may vary freelywithin the scope of the appended claims. For example, instead of usingan input rectifier 107 as described above, any suitable DC input may beused, such as for example a battery.

Furthermore, the power input 102 may be arranged for receiving an inputvoltage from an engine-driven generator, where the generator is of thesame type as the electric motor 136. The electric motor 136 is forexample in the form of a brushless direct current, BLDC, motor, whichmay be of a synchronous type.

The control unit 134 may be arranged to detect if the neutral connectionis present at the power input 102, the control unit 134 further beingarranged to control the output voltage in dependence of the presence ofsaid neutral connection. For example, if there is no neutral connection,the output power may be reduced.

The control unit may further be arranged to detect if electrical poweris present at the alternating current power ports 110, 111, 112, thecontrol unit 134 further being arranged to control the output voltage independence of the loss of said phase connection. For example, if thereare alternating current power ports lacking electrical power, the outputpower may be reduced.

For a three phase system, the voltages at the alternating current powerports 110, 111, 112 have a phase difference of 120 degrees, which makesthe rectified incoming voltage smooth and steady. If one or two phasesare missing at the alternating current power ports 110, 111, 112, therectified voltage pulses and the instantaneous amount of power that ispossible to acquire from mains outlet varies with the incoming voltageperiod. The amount of power that is possible to utilize depends on thephase difference between the incoming lines.

A three phase power cord typically consists of five wires: a protectiveground port, the neutral port 113 and the three alternating currentpower ports 110, 111, 112. However, in some installations, the neutralport 113 and one of the alternating current power ports 110, 111, 112can be mixed up. There are also systems that do not supply a neutralport, leaving it floating. Alternatively, one of the alternating currentpower ports 110, 111, 112 can be connected to one or two of the otherports, making an apparently valid voltage appear on two or three ports.However, since the phase in that case is the same for those ports, it isnot possible to utilize the provided power to its full extent. Anotherproblem is a possible voltage potential difference between theprotective ground port and the neutral port 113, which makes itdifficult to have a good voltage reference level for the voltagemeasurements.

In order to handle the above, the control unit 134 is arranged toanalyze the connected ports and determine how much power that it ispossible to acquire. The main analysis is performed by means of asoftware algorithm that in general works like described below.

The algorithm starts by measuring all incoming phases on the alternatingcurrent power ports 110, 111, 112 and the neutral port 113 relative aninternal voltage reference. With reference to FIG. 17, showing aschematical illustration of the power ports and voltages available in athree-phase system, all possible main voltages are calculated; thecorresponding voltages on the alternating current power ports 110, 111,112 are referred to as V₁₁₀₋₁₁₁, V₁₁₁₋₁₁₂ and V_(112-110.)

Since it is not known whether the neutral port 113 has been exchangedwith any of the alternating current power ports 110, 111, 112, the mainvoltage candidates are V₁₁₀₋₁₁₁, V₁₁₁₋₁₁₂ and V₁₁₂₋₁₁₀. V₁₁₀₋₁₁₃,V₁₁₁₋₁₁₃ and V₁₁₂₋₁₁₃. Each main voltage candidate is determined to bequalified by having a signal magnitude elevated from the noise and avalid period. Then, the largest of these is assumed be a valid firstmain voltage, or for single phase, the one and only phase voltage. Forthe remaining voltages, the phase relation to the first main voltage isdetermined by analysis in time domain. If the considered candidatevoltage has a phase relation of ±120° relative the first main voltage,it is determined to be a second main voltage.

At the end of the analysis, 1-3 voltages have been acquired, each withits own phase. Using that information, a judgment about the availablepower can be made and signaled to the tool 106, for example to the toolcontrol unit 140.

It is thus possible to use the tool 106 in a controlled manner for a lotof different electrical configurations spanning numbers of input phases,voltages and voltage potential relative protective ground.

The above does not require a three-phase system with a neutralconnection, but requires in its most uncomplicated form a power input102 comprising at least two ports 110, 111, 112, 113 between which thereis a voltage potential. This voltage potential does not have to bealternating.

Generally, the control unit 134 is arranged to determine the voltagebetween each port comprised in the power input 102, and to select thosevoltages that exceed a predetermined threshold value during a certaintime period, the control unit 134 further being arranged to compare thephase relations of the selected voltages and based on this comparisondetermine the amount and composition of available power.

The control unit 134 is furthermore arranged to communicate the amountand composition of available power, enabling control of the motor independence of the amount and composition of available power.

The algorithm may be at least partly implemented in the control unit 134and/or the tool control unit 140. As shown in FIG. 18, the power input102 is shown to comprise an input analyzer 157 that is connected to thecontrol unit 134. Other arrangements are of course conceivable.

With reference to FIG. 19 showing a flowchart, the above is performed bymeans of a general method for providing an estimate of available powerto an electrically powered tool 106, the method comprising the steps:

152: measuring all voltages between all ports at a power input 102 withat least two ports 110,111, 112, 113 between which there is a voltagepotential;

153: determining all possible voltages between said ports 110,111, 112,113;

154: selecting those voltages that exceed a predetermined thresholdvalue during a certain time period;

155: comparing the phase relations of the selected voltages and based onthis comparison determine the amount and composition of available power;and

156: communicating the amount and composition of available power to theelectrically powered tool 106.

As mentioned above, said voltage potential between ports 110,111, 112,113 does not have to be alternating, but may of course be alternating.

The control unit 134 may further be arranged to detect if the tool 106is connected to the tool interface 103, and if that is the case, toindicate at a display 147, comprised in the power supply device 100,what type of electrically powered tool 106 that is connected to the toolinterface 103. At the display 147 there may be user control buttons (notshown), which for example may be used for choosing different functions.Other messages, such as for example present power supply and errormessages, may be indicated in the display 147.

As shown in FIG. 12, it has been assumed that the power supply device100 is separate and easily detachable from the tool 106, but it is alsoconceivable that the power supply device 100, or at least some of itsparts, instead are integrated into the tool 106, for example as shownwith reference to FIG. 16. Other alternatives are of course conceivable,even the case where all parts of the power supply device 100 areintegrated into the tool 106.

Furthermore, the power supply device 100 may comprise a residual currentdevice 50 arranged to break the circuit in the case of a currentimbalance in a previously known manner. The residual current device maybe comprised in the power input 102, or may be constituted by a separatedevice 50, as shown in FIG. 1.

All figures disclosed are to be regarded as examples only, for examplethe voltages disclosed may of course vary in order to be of a suitablemagnitude.

The electric motor 136 may be an asynchronous motor as well as asynchronous motor.

The converter assembly 133; 133′, either in its entirety or at leastpartly, is commonly known as a power booster or a voltage booster.

When it is indicated that the neutral port 113 is connected to a voltagethat in normal conditions is the average of the voltages of saidalternating current power ports 110, 111, 112, this is not to beinterpreted as a mathematically exact average, but as an average withinwhat is practical in this context. It may be regarded as essentiallybeing the average of the voltages of said alternating current powerports 110, 111, 112.

The invention claimed is:
 1. An electric power saw comprising: arotatable saw structure a rear handle with a switch control a fronthandle a drive unit for rotating the saw structure, the drive unitcomprising: a saw structure drive arrangement to which the saw structureis attachable a transmission for driving the saw drive arrangement anelectric motor for driving the transmission a support structure forholding the saw structure drive arrangement, the transmission and theelectric motor, and a fluid control unit arranged to regulate anddistribute a fluid through a plurality of conduits, wherein the fronthandle and the rear handle are directly connected to each other to forma handle unit, which is resiliently connected to the drive unit, so thatvibrations from the saw structure and drive unit are reduced in thehandle unit, and the power saw includes a cooling fluid systemcomprising: at least one the cooling path in the motor, having an inletfor connecting to a fluid source and an outlet, said cooling pathrunning within a side wall of a motor housing that is parallel to arotor axis of the motor, wherein the motor housing comprises an innertubular part and an outer tubular part, wherein the cooling path isdisposed between the inner tubular part and the outer tubular part,wherein the rear handle further includes a trigger lock opposite to theswitch control, the trigger lock activating the switch control when thetrigger lock is actuated, the trigger lock further opening an inletvalve of the fluid control unit when being actuated and returning theinlet valve to a closed position when the trigger lock is not actuated,and wherein the fluid control unit includes a transfer conduit whichconnects to the outlet and includes a fluid valve configured to directfluid from the motor to a tool conduit leading to at least one nozzle atthe rotatable saw structure and/or to a return conduit to discard orreturn a remaining flow to the fluid source.
 2. An electric power sawaccording to claim 1, wherein the rotatable saw structure is onecircular saw blade and the saw structure drive arrangement is a sawblade drive shaft.
 3. An electric power saw according to claim 1,wherein the rotatable saw structure is formed by two circular saw bladesat an axial distance from each other and the saw structure drivearrangement is a common saw blade drive shaft driving both saw blades.4. An electric power saw according to claim 1, wherein the rotatable sawstructure is a ring saw blade and the saw structure drive arrangement isa ring saw aggregate.
 5. An electric power saw according to claim 1,comprising an anti-vibration handle system comprising vibration-dampingelements positioned between the handle unit and the drive unit.
 6. Anelectric power saw according to claim 5, wherein said anti-vibrationhandle system comprises at least three vibration-damping elements.
 7. Anelectric power saw according to claim 5, wherein at least one of thevibration-damping elements is a resilient element.
 8. An electric powersaw according to claim 1, wherein the electric motor is a highfrequency, permanent magnet motor having the motor housing surrounding astator and a rotor.
 9. An electric power saw according to claim 1,wherein the cooling path runs in the side wall in a circular helixaround the stator housed in the motor housing.
 10. An electric power sawaccording to claim 1, wherein the fluid control unit includes a toolconduit valve downstream the inlet valve that can be gradually adjustedby an operator between a fully closed position and a fully openedposition, said tool conduit valve leading to the tool conduit.
 11. Anelectric power saw according to claim 1, wherein the fluid control unitincludes a return conduit valve downstream the inlet valve that can beset in at least two modes by an operator, an open mode for returningfluid to the return conduit and a closed mode for blocking fluid flow tothe return conduit.
 12. An electric power saw according to claim 1,wherein the transmission is a belt transmission.
 13. An electric powersaw according to claim 1, wherein the cooling path is formed by a groovein the inner tubular part.
 14. An electric power saw according to claim1, wherein an outer diameter of the inner tubular part is substantiallyequal to an inner diameter of the outer tubular part, such that theinner tubular part is insertable into the second tubular part.
 15. Anelectric power saw comprising: a rotatable saw structure a rear handlewith a switch control a front handle a drive unit for rotating the sawstructure, the drive unit comprising: a saw structure drive arrangementto which the saw structure is attachable a transmission for driving thesaw drive arrangement an electric motor for driving the transmission asupport structure for holding the saw structure drive arrangement, thetransmission and the electric motor, and a fluid control unit arrangedto regulate and distribute a fluid through a plurality of conduits,wherein the power saw includes a cooling fluid system comprising: acooling path in the motor, having an inlet for connecting to a fluidsource and an outlet, said cooling path running within a side wall of amotor housing that is parallel to a rotor axis of the motor, wherein themotor housing comprises an inner tubular part and an outer tubular part,wherein the cooling path is disposed between the inner tubular part andthe outer tubular part, wherein the rear handle further includes atrigger lock opposite to the switch control, the trigger lock activatingthe switch control when the trigger lock is actuated, the trigger lockfurther opening an inlet valve of the fluid control unit when beingactuated and returning the inlet valve to a closed position when thetrigger lock is not actuated, and wherein the fluid control unitincludes a transfer conduit which connects to the outlet and includes afluid valve configured to direct fluid from the motor to a tool conduitleading to at least one nozzle at the rotatable saw structure and/or toa return conduit to discard or return a remaining flow to the fluidsource.
 16. An electric power saw comprising: a rotatable saw structurea rear handle with a switch control a front handle a drive unit forrotating the saw structure, the drive unit comprising: a saw structuredrive arrangement to which the saw structure is attachable atransmission for driving the saw drive arrangement an electric motor fordriving the transmission a support structure for holding the sawstructure drive arrangement, the transmission and the electric motor,and a fluid control unit arranged to regulate and distribute a fluidthrough a plurality of conduits, wherein the power saw includes acooling fluid system comprising: a cooling path in the motor, having aninlet for connecting to a fluid source and an outlet, said cooling pathrunning within a side wall of a motor housing, wherein the rear handlefurther includes a trigger lock opposite to the switch control, thetrigger lock activating the switch control when the trigger lock isactuated, the trigger lock further opening an inlet valve of the fluidcontrol unit when being actuated and the trigger lock returning theinlet valve to a closed position when the trigger lock is not actuated,and wherein the fluid control unit includes a transfer conduit whichconnects to the outlet and includes a fluid valve configured to directfluid from the motor to a tool conduit leading to at least one nozzle atthe rotatable saw structure and/or to a return conduit to discard orreturn a remaining flow to the fluid source.